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Plug-in hybrid electric vehicles release nearly five times greater planet-heating pollution than lab-reported data show, according to a new report.

Widening Gap Between Lab and Real-World CO2 Output

Statistics shows that PHEVs release only one-fifth lower CO₂ than conventional petrol and diesel cars, according to analysis conducted by a non-profit organization. This contrasts sharply with lab estimates, which suggested a 75% decrease in pollution.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” stated a senior researcher involved in the report. “That gap is widening and poses a serious problem. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Key Factors Driving the Discrepancy

Analysts linked most of the difference to overestimates of the “utility factor” – the ratio of miles driven in battery mode relative to total distance. They found that just a quarter of travel was completed in electric mode, whereas lab assumptions assumed over four-fifths.

Even, when operating in EV mode, pollution levels were significantly higher than official estimates. That happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors burning fossil fuels for almost a third of the distance covered in electric mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV CO2 output allowed several major carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay about €500 extra annually in operating costs than would be assumed under lab conditions.

“The bold claims that manufacturers often promote about their PHEV vehicles are obviously way off the truth,” stated a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have lately been brought again into political debates as automakers have pressed the EU to relax CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced intense lobbying from the car industry and opposition from member states with significant car industries.

Several high-level politicians have suggested PHEVs as a possible “compromise” solution to include in the regulation.

One independent energy policy specialist, who was unaffiliated with the study, described the report a “very useful contribution” after years in which segments of the automotive industry argued there was insufficient information to properly evaluate actual CO2 output.

“These findings demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel cars,” they stated. “Any policy changes concerning PHEVs should be implemented with extreme care and in the light of this data.”